1. Field of the Invention
This invention relates to a front frame structure for a vehicle.
2. Description of the Prior Art
Generally, the front side frame of a vehicle has a side frame portion mounted on the side wall of the engine compartment to extend in the longitudinal direction of the vehicle body, and a floor frame portion which is disposed on the rear side of a dashboard frame positioned on the rear end of the engine compartment and mounted on the lower surface of a floor panel to extend in the longitudinal direction of the vehicle body.
In order to lower the floor of the passenger compartment, the floor frame portion is generally positioned lower than the side frame portion, and accordingly the junction of the side frame portion and the floor frame portion makes a bent portion inclined downward toward the rear of the vehicle body. Further, the side frame portion is generally channel-shaped in cross-section with the open portion upward on purpose to mount the floor panel on the top thereof.
In such a front side frame in which the junction of the side frame portion and the floor frame portion is bent and the floor frame portion on the rear side of the bent junction has an open cross-section of a relatively low buckling strength, the bent junction of the side frame portion and the floor frame portion is apt to buckle in a head-on collision in which the collision load acts on the front side frame from the front end of the vehicle body.
Though a reinforcement is provided in the front side frame, it is difficult to form the reinforcement as a one-piece member since the side frame portion and the floor frame portion are connected by way of the bent junction and differ from each other in cross-section. Accordingly the reinforcement is generally formed as two members, one being a front reinforcement for the side frame portion and the other being a rear reinforcement for the floor frame portion, and the front reinforcement and the rear reinforcement are connected to each other near the bent junction of the front side frame.
However, axial forces, bending forces, shearing forces and the like act on the bent portion of the front side frame in a complex combination in a head-on collision of the vehicle body, and accordingly there is a risk that the junction of the front reinforcement and the rear reinforcement will be broken by such a collision.
Though not intended to increase the strength of the front side frame, there has been disclosed in Japanese Unexamined Patent Publication No. 58(1983)-214478 a front side frame structure in which a partitioning plate is provided in the front side frame to extend in the longitudinal direction thereof and separate the inner space of the front side frame into two spaces. With this arrangement, although the strength of the front side frame is increased to some extent, it is not satisfactory.